Annular spinning apparatus



March 7, 1967 A. DUNN ETAL 3,307,216

ANNULAR SPINNING APPARATUS Filed Oct. 5, 1964 F/GURE //7 1/6 0 fors A/berf Dun/v Lu/her Passe/l BY $351k V A ffomey United States Patent ()fitice 3,3fi'LZlfi Patented Mar. 7, 1967 3,307,216 ANNULAR SPINNING APPARATUS Albert Dunn, Kings Mountain, and Luther Russell, Gastonia, N.C., assiguors to Fiber Industries, Inc., a corporation of Deiaware Filed Oct. 5, 1964, Ser. N 401,498 2 Claims. (Cl. 188) This invention relates to a new and useful apparatus for the production of filaments and the like from a synthetic polymeric material and more particularly, to an improved melt spinning pack for the melt extrusion of filaments from synthetic linear polymers such as, polyamides, polyesters, polyolefins and the like.

In the melt spinning of fibers, it is usual to filter the molten polymer before extrusion by forcing it through a filter bed of inert granular material support d by a gauze before it reaches the spinneret. The purpose of the filtration of the molten polymer is to p event incompletely fused polymer, foreign matter, aggregates of delustering materials and the like from reaching the spinneret. During the molten polymer filtration process which is usually conducted under pressure, the filter bed during its use requires increasing pressure to force the molten material through the bed due to the collection of filtered solid material within the bed. The life of the filter bed and spinning pack is greatly dependent on the total pressure which can be tolerated du'ing operation. It is .weEl known that as the sp'nning peck pressure increases, various undesirable occurrences can take place such as variations in intrapack temperatures and melt distribution, channeling of the bed of granular material, pump slippage at high back pressures, and the like. To overcome some of the difficulties de'crbed ab ve associated with conventional spinning packs, it would be highly desirable to utilize a larger filtraton surface area than is normally used within the granular beds and thereby significantly prolong the life of the granular bed and spinning pack. In order to increase the surface area of the conventional filter bed within the conventional spinning packs, the size of the spinning packs must be appropriately increased. This increase in size of the spinning equipment must be significantly changed to accommodate the larger spinning pack.

It is the over-all object of the present invention to provide an improved melt spinning pack over the known conventional types. The distinct advantages of the melt spinning pack of this invention over the known types are numerous and include, among others: 1) a larger surface area of filtration within substantially the same confined area; (2) a lower pressure drop as the molten polymer passes through the melt spinning pack; (3) an improved uniformity of flow path; (4) no stagnant zones; (5) improved heat interchange; (6) a relatively thin bridge plate is required; (7) a greatly reduced total force acting on the bottom and top of the pack is present when passing molten polymer through; (8) a low volume of granular inert material such as sand is required; (9) the temperature difference across the granular bed is minimized because of the construction of the spinning pack of this invention. These and other objects and advantages will become apparent from the following description and accompanying drawing in which:

FIGURE 1 is a side view crosssection of a preferred embodiment of this invention describing an annular shaped melt spinning pack;

FIGURE 2 is a top view of the apparatus of FIGURE 1 taken at 22 to demonstrate the shape of the melt spinning pack.

The melt spinning pack of this invention is unique in the manner in which the molten polymer can be fed and withdrawn from the granular inert material used for filtration. The inlet means for the molten polymer is placed in such a manner so as to surround the outer perimeter of the granular bed except for that area lying adjacent to and in a parallel plane to the spinneret. On the other hand, the outlet means for the molten polymer is placed in a corresponding manner at the internal base of the granular bed to that of the inlet means so that the granular bed has substantially a uniform depth from the corresponding points in the inlet and outlet means which are in the same plane. Under these conditions, the molten polymer will fill completely the inlet means before going through the granular bed. At that point, a particle of the polymer will flow from the point in the inlet means in substantially the same plane from that point through the granular bed to the outlet means since this is the path of least resistance. Theoretically, a particle of molten polymer will be treated identically throughout the entire granular bed and establish a uniform flow path without any stagnant zones being present. Furthermore, the arrangement of the granular bed between the inlet means and outlet means described above will also provide a larger surface area of filtration within substantially the same confined area of the conventional spinning pack. Furthermore, in view of a larger surface area of the granular material as well as a smaller amount of granular material in the spinning pack of this invention over that of the conventional spinning pack, alower pressure drop of the molten polymer is present as it passes through the melt spinning pack. These important features are readily recognized by those skilled in the art.

FIGURE 1 describing a preferred embodiment of the melt spinning pack of this invention is found to be especially useful in spinning highly viscous polymers. The melt spinning pack has an outer and inner ring 11 and 9, respectively, with a top cover 8. The combination of the outer and inner rings 11 and 9, with the top cover 8, comprises the body of the met spinning pack which contains spinneret orifices 1th confined in annular shape around an inner space void 18. The melt spinning pack contains outlet means or channels 20 formed by a bridge plate 13 and an inner wire gauze filter 14. The inner wire gauze 14 holds the inner granular material in the filter bed 12 while the outer corrugated ring 15 acts as the inlet means and channels for the molten polymer to the filter bed 12 and also holds the outer granular material of the filter bed 12;. It should be noted that the inner wire gauze 14 and outlet means is in a corresponding spaced relation with the outer corrugated ring 15 or inlet means to provide a granular bed having a substantially uniform depth. The filter bed 12 is shaped in the form of a cross-sectional inverted U wherein the outer perimeters of the U-shaped unit contain the inlet means and the closed base of the cross-sectional U-shaped perimeters is initially contacted by the molten polymer. On the other hand, the inner perimeter of the cross-sectional U-shaped filter bed 12 contains the outlet means which provides channels to the spinneret at the open end of the U-shaped unit for permitting flow of the molten polymer to be spun from the spinneret. The molten polymer enters the spinning pack at entrance 17 and enters channel 21 through pipe 16. After the channels 21 are filled with molten polymer, the inlet means 15 are then filled as described above. The melt spinning pack is essentially heated from an outer source, not shown, in which the spinning pack is placed, but in addition, has an inner heating unit 19 to supply a more uniform distribution of heat.

The shape of the preferred embodiment of this invention has the appearance of an annular or ring-like shaped doughnut with the hole or space void in the center of the pack. Utilizing this shape provides accessibility to the inner row of extruded threads through the center of the spinning pack as well as heating the inner portions of the pack. When compared on the same over-all size dimensions, it should be readily apparent that the surface and filtration area of the granular bed in the appara tus of FIGURE 1 is significantly increased by utilizing an annular shape over the surface and filtration area of a granular bed of the same depth of a spinning apparatus normally used which is not confined in an annular shape. It should also be noted that the shape of the granular bed within the annular spinning pack is not necessarily critical but for purposes of this invention, it is essential that the granular bed have a substantially uniform depth.

As an example of reduced back pressures, polyethylene terephthalate polymer having a viscosity of 9000 poises was extruded through the annular melt spinning pack as described in FIGURE 1 of the accompanying drawing, at a throughput of 42 pounds per hour. The initial spinning pressures were 1100 pounds per square inch gauge compared to 3000 pounds per square inch gauge utilizing a nonannular conventional melt spinning pack of a comparable size.

The material of construction for the melt spinning pack of this invention can be any type of metal normally used for this type of pack. The inert granular material which can be used in the filter beds or granular beds can be various types of finely divided material such as sand, steel balls, iron filings, stainless steel fil'ngs, glass beads and similar inert substances. It is preferred, however, to use silica sand since it is relatively cheap, inert and does not tend to matt down and stop the openings of the metal gauze.

The apparatus of this invention is particularly suitable for the melt spinning polymers which can be highly viscous such as polyethylene terephthalate, nylon, polyolefins, and the like.

It is to be understood that the foregoing description is merely illustrative of preferred embodiments of the invention of which many variations may be made by those skilled in the art Within the scope of the following claims Without departing from the spirit thereof.

What is claimed is: r

1. An annular melt spinning pack having a spinneret containing a plurality of orifices for shaping filamentforming material as molten polymer is extruded therethrough wherein said spinning pack is internally confined in an annular shape surrounding an external space void,

a granular bed of finely divided inert material contained Within said spinning pack, inlet means for said molten polymer surrounding the outer perimeter of said granular bed other than the perimeter lying adjacent to and in parallel plane to said splnneret, outlet means for said molten polymer establishing a base for said granular bed in a correesponding spaced relationship with said inlet means to provide a substantially uniform depth of said inert material throughout said granular bed between said inlet means and said outlet means and collecting means for said molten polymer in the form of an internal annular space in said spinneret pack connecting said outlet means and said spinneret orifices.

2. An annular melt spinning pack having a spinneret containing a plurality of orifices for shaping filamentforming material as molten polymer is extruded therethrough wherein said spinning pack is internally confined in an annular shape surrounding an external space void, a cross-sectional inverted U-shaped granular bed of finely divided inert material contained within said spinning pack, wherein the closed portion of said cross-sectional inverted U-shaped granular bed is placed in the initial direction of polymer flow, inlet means for said molten polymer surrounding the outer perimeter of said crosssectional inverted U-shaped granular bed, outlet means for said molten polymer surrounding the inner portions of said cross-sectional inverted U-shaped granular bed in a corresponding spaced relations-hip with said inlet means to provide a substantially uniform depth of said inert material throughout said granular bed between said inlet means and outlet means, and collecting means for said molten polymer in the form of an internal annular space in said spinneret pack connecting said outlet means and said spinneret orifices.

References Cited by the Examiner UNITED STATES PATENTS 2,881,474 4/1959 Sellers et a1. 18-8 2,936,482 5/1960 Kilian 18-8 3,104,419 9/1963 LaForge 18-8 3,204,289 9/1965 Barlow et al. 18-8 FOREIGN PATENTS 329,975 12/ 1920 Germany. 3 67,591 4/ 1963 Switzerland.

WILLIAM J. STEPHENSON, Primary Examiner. 

1. AN ANNULAR MELT SPINNING PACK HAVING A SPINNERET CONTAINING A PLURALITY OF ORIFICES FOR SHAPING FILAMENTFORMING MATERIAL AS MOLTEN POLYMER IS EXTRUDED THERETHROUGH WHEREIN SAID SPINNING PACK IS INTERNALLY CONFINED IN AN ANNULAR SHAPE SURROUNDING AN EXTERNAL SPACE VOID, A GRANNULAR BED OF FINELY DIVIDED INERT MATERIAL CONTAINED WITHIN SAID SPINNING PACK, INLET MEANS FOR SAID MOLTEN POLYMER SURROUNDING THE OUTER PERIMETER OF SAID GRANULAR BED OTHER THAN THE PERIMETER LYING ADJACENT TO AND IN PARALLEL PLANE TO SAID SPINNERET, OUTLET MEANS FOR SAID MOLTEN POLYMER ESTABLISHING A BASE FOR SAID GRANULAR BED IN A CORRESPONDING SPACED RELATIONSHIP WITH SAID INLET MEANS TO PROVIDE A SUBSTANTIALLY UNIFORM DEPTH OF SAID INERT MATERIAL THROUGHOUT SAID GRANULAR BED BETWEEN SAID INLET MEANS AND SAID OUTLET MEANS AND COLLECTING MEANS FOR SAID MOLTEN POLYMER IN THE FORM OF AN INTERNAL ANNULAR SPACE IN SAID SPINNERET PACK CONNECTING SAID OUTLET MEANS AND SAID SPINNERET ORIFICES. 